Join Date: Nov 2007
Location: NYC & Long Island, NY
There's not much sense in adding more gravel, since most of the easy plants that grow best in low-light can be anchored onto driftwood and rocks (anubias, moss, java ferns, etc).
Like Laura said, I'd go hunting through this forum and other forums and see what's attractive for you. Even if you find a high-light setup that you can, you can probably adjust it to low-light by doing some plant switches. In your case, Id start with a solid hardscape--rocks and driftwood--and work from there.
Regarding your xmas moss... couldnt say for certain, but mosses usually take a while to acclimate in my tanks, but once they start growing, they dont stop. I believe Xmas moss take on its best form (with evergreen-like fronds) when it's anchored to something. I'd try tying some of yours to your rocks, to see if you like its anchored-growth better than the loose free-floating growth.